Neumann Vintage U87 Clone : Build Thread.

[RuudNL]

Yesterday I took a closer look at the U87 schematic, and (I think) I saw something strange:
In the low-cut position, a 150K resistor bypasses the 1M/160 (or 220) pF HF frequency correction.
IMHO this means that the HF correction is more or less disabled when the low-cut is active.
As far as I know I never heard somebody talking about this, but doesn't this mean: LF-cut is also HF-boost?

 

[mus1k_freak]

ok so i cant get my u87 working, i have no sound at all, if i touch where the capsule connects i get crackles and hum or if i touch any of the grounding points it hums real loud, does anything look obviously wrong from these pictues? ive read through the thread for a few days now and cant seem to find anything, i bought the boards pre stuffed from another member but everything looks like (besides i had to lift the gate on the fet)

 

[kante1603]

Hello,

sadly I must say that this is a really ugly soldering job throughout.Nearly all solder joints seem to be dirty or cold,parts legs standing off,lots of residual flux everywhere,badly soldered wires.......
The pics are not good enough to go on here.
If you really want to proceed try to make some better ones,from my experience it works pretty good to put the boards on a scanner.Just cover them with some preferably dark cloth,then scan.
To give it a new start I personally would desolder all wiring.Then try to resolder all necessary points with fresh solder and a good iron.Then clean the board with isopropylene alcohol as good as possible.
Remember styrenes absolutely don't like that,so please be carefull!
The omni jumper is not needed at the moment.

I can't tell if all parts have survived this job from the former builder,sorry.

Otherwise try to get your money back,why not start a new one......

About humming etc.,as long as the boards aren't in the good grounded mic body it will hum and pic up tons of rf noise anyway.
And you should never touch anything in the high impedance area with bare fingers!
Keeping it as clean as possible is imperative.

Tell us what you'll do,

best regards,

Udo.

 

[kante1603]

Yesterday I took a closer look at the U87 schematic, and (I think) I saw something strange:
In the low-cut position, a 150K resistor bypasses the 1M/160 (or 220) pF HF frequency correction.
IMHO this means that the HF correction is more or less disabled when the low-cut is active.
As far as I know I never heard somebody talking about this, but doesn't this mean: LF-cut is also HF-boost?

Hi Ruud,

I must say that I nearly never use cuts on mics,only those from the preamps or consoles,mostly because of better choice of cutting frequencies there.But I can give it a try next time I use them in the studio and monitor it.Having a huge live job atm,so it will take some time.

Best regards from germany,

Udo.

 

[3nity]

@ musik_freak
As Kante put it, you really need to get better at soldering.
You probably seem to have the same issues as the Germanium preamp from PPA.
Good luck!

 

[mus1k_freak]

I'll try resoldering some of the joints,  this one I got  pre-built and fixing a few of the errors made things a little messy,  I've built probably over 100 things with very few issues, desoldering and resoldering is what kills me always ends up  a mess 

 

[bockaudio]

Yesterday I took a closer look at the U87 schematic, and (I think) I saw something strange:
In the low-cut position, a 150K resistor bypasses the 1M/160 (or 220) pF HF frequency correction.
IMHO this means that the HF correction is more or less disabled when the low-cut is active.
As far as I know I never heard somebody talking about this, but doesn't this mean: LF-cut is also HF-boost?

No! It's only a low cut. The cap, which is the HF cut, does not change.
If you want more HF cut increase that cap, the LF cut will still work.

 

[jameswenzel]

Hi all, just tried to assemble mine last night, to no avail.
Not sure if it's the components I used, a bad component, or a soldering job... I'll just throw things out there in case any of you think you'd be able to help.

These are the parts I used. It's not the list on the first page of the thread (have a feeling this might be the problem), but it's a list put together by the guy who made the video blog tutorial: https://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=1da9f2a856

Also, something strange: when trying to bias the FET, the voltage between the drain/body is VERY unstable. It fluctuates between 7-15V~ over time (it might take a couple minutes to get from one end to the other).
Crudely injecting a signal through an audio interface, with output back into my audio interface (via 1/4" cables) to look at through a software oscilloscope yields a tiny sine wave that turns triangle on increased volume (probably not the best way to go about this, just was frustrated with the multimeter method and unstable voltage). With no signal injected there is a low hum.

If anyone has any ideas, I'd be greatly appreciative.

 

[sr1200]

@jameswenzel: post some pics or links to pics of your boards.  Would be a lot easier to see a problem.

 

[jameswenzel]

@jameswenzel: post some pics or links to pics of your boards.  Would be a lot easier to see a problem.

Will do. I think I fixed the voltage problem after resoldering the components. I plan on redoing the wires from the switches/etc after work tonight. Will update with pics if it still doesn't work after that.

 

[jameswenzel]

It works! Resoldering fixed the FET voltage problem. I built it into an MXL 2010 body and was having trouble with the wiring to the switches. Accidentally soldered the low cut/pad leads to the wrong spots... but I fixed it! And it sounds GORGEOUS!
Though I did notice a strange, quiet low noise at first. I took off the body, took a peek at the wires and when I closed it back up it was gone. My old mic had the same noise sometimes... maybe it's on the interface end.  Anyone have any ideas as to what that might be? I'll try to capture it if it does it again.

 

[Caiwyn]

I put together a makeshift oscilloscope with an iRig and an iPhone: http://www.youtube.com/watch?v=Y8C6ac7UrHI

I'm also using the test oscillator plugin in Logic Pro to generate a 1kHz tone and sending that from the headphone jack on my laptop to a pair of alligator clips.  The ground is connected to the mic chassis and the center conductor is connected to the bottom of R6.

Just a follow-up, since there was some interest in whether this would work.  It did not fry my phone or my laptop.  The iRig does a barely serviceable job of reading the signal, however.  The iRig HD provides a much cleaner input, and adjustable gain.  Everything was clearer and more precise than the DSO Nano v3 oscilloscope, but the DSO Nano was able to handle the test tone at higher amplitudes.  So I started with the makeshift iPhone oscilloscope, and then fine-tuned with the DSO Nano.  I wound up at just over 10v at the FET drain.  Does that sound reasonable?

Although the oscilloscope app on the iPhone does include a test tone generator, it's far too weak to be used through the iPhone's headphone output alone.  You'd have to have it amplified somehow.  I used the Logic test oscillator plugin and output the signal from my laptop's headphone jack, which worked well.  The DSO Nano includes a square wave generator, but no sine wave, so its output could not be used.

 

[poctop]

10v at the FET drain.  Does that sound reasonable?

if you can see the sine gets squared off at the peak on both top bottom as you are ajusting the Pot then.....

what you see is what you get 

No Fet will give the same bias voltage.
but they can range from 8 to 13V
you can measure also the source Voltage and use the value of R*  your pot to determine the idle current.

Hope this helps,
But I salute the tecnical efforts with the IO stuff,
Best,
Dan,

 

[GonzoConMojo]

Hello everyone,

I used Dany's PCB, a B2 Pro Body and an AMI T13 to build one (or hopefully soon two) of my own delicious sounding U87. As I have travelled a long way through this thread and now should say that I have completed my first ever U87, I instead encounter troubles: I don't get the tiniest bit of a signal out of the U87.

Frustrated and confused I got back to the construction site and double checked all soldering points, disconnected all switches, re-soldered the XLR (just in case I swapped the pins as I sometimes do for a reason only my brain knows) and now I even think of de-soldering the AMI and check if it is connected right (of what I am not exactly sure as this little unit's wires are not too easy to sort out). I even tried (re-)calibrating the trimpot by measuring the amount of V on FET Source. Fact is, that I get an amount of 0V on the drain voltage, while I get quite a stable 18V on "hot", top of R18 as well as the FET source. 18V are transportet through the XLR Connector's Pins while my Phantom Power Unit (a small mixing console) produces an amount of 47.8 V. What the heck is going on?

I am most thankful for any advice.

Best,
Bodo

 

[poctop]

Hello everyone,

I used Dany's PCB, a B2 Pro Body and an AMI T13 to build one (or hopefully soon two) of my own delicious sounding U87. As I have travelled a long way through this thread and now should say that I have completed my first ever U87, I instead encounter troubles: I don't get the tiniest bit of a signal out of the U87.

Frustrated and confused I got back to the construction site and double checked all soldering points, disconnected all switches, re-soldered the XLR (just in case I swapped the pins as I sometimes do for a reason only my brain knows) and now I even think of de-soldering the AMI and check if it is connected right (of what I am not exactly sure as this little unit's wires are not too easy to sort out). I even tried (re-)calibrating the trimpot by measuring the amount of V on FET Source. Fact is, that I get an amount of 0V on the drain voltage, while I get quite a stable 18V on "hot", top of R18 as well as the FET source. 18V are transportet through the XLR Connector's Pins while my Phantom Power Unit (a small mixing console) produces an amount of 47.8 V. What the heck is going on?

I am most thankful for any advice.

Best,
Bodo

Might some picture of your build be helpfull,
when complex problems arise the easiest solution are always the best,
you should be able to measure the full 48V at the input of the mic for phantom power .,
make sure you have the xlr wired correclty . it is on the silkscreen small but there ,
pin 1 = gnd
pin 2 hot
pin 3 cold ,
remove transformer lead and measure again ,
check all the reference voltage with the transfomer unhooked ,
hope this helps,
Best,
daN,
dD

 

[rob61]

Thinking of replacing my vintage U-87 capsule with a Beezneeze K8 capsule to use while I get my original reskinned. This is a direct replacement I'm told. Would I have to recalibrate the FET electronics once I mount the new capsule as you need to do when you build a new one?

 

[poctop]

Thinking of replacing my vintage U-87 capsule with a Beezneeze K8 capsule to use while I get my original reskinned. This is a direct replacement I'm told. Would I have to recalibrate the FET electronics once I mount the new capsule as you need to do when you build a new one?

No you dont need to re-Bias the Fet as this is power and FET dependant, the actual bias is actually done without the capsule installed ,
Best,
Dan,

 

[micaddict]

Wink0195 wrote:

I will be posting pics about how i made the b2-pro body suitable for this build considering it was quite a hassle to work in, but I figured I'd take the pics during my 2nd diy u87 build considering I bought 2 kits of diy u87 parts. I can even make a brief step by step guide for working with the b2-pro body.

Please do! 

I assume you used the smaller (tapered) PCB?
From what I remember, a couple of others used the Behringer B2 Pro as well. But there are different versions, the older ones having a detachable head with a thick, plastic, receiving or female disc. Consequently, there'll be a little less room in those.


Henk

 

[MetalD]

Hi, I'm new to this whole deal and I only have access to a cheap multimeter. I know that R18 and R19 need to be matched to .4% and I simply do not have access to the resources to do this. Can someone tell me if these would work as a suitable replacement?

http://www.mouser.com/Search/ProductDetail.aspx?R=PTF652K2000BZBFvirtualkey61300000virtualkey71-PTF652K2000BZBF

Thanks,

MetalD

 

[kante1603]

Hi, I'm new to this whole deal and I only have access to a cheap multimeter. I know that R18 and R19 need to be matched to .4% and I simply do not have access to the resources to do this. Can someone tell me if these would work as a suitable replacement?

http://www.mouser.com/Search/ProductDetail.aspx?R=PTF652K2000BZBFvirtualkey61300000virtualkey71-PTF652K2000BZBF

Thanks,

MetalD

Hello and welcome to the forum.
I wanted to suggest exactly that,if in doubt try 0,1% precision type resistors.
A bit on the high side pricewise though.....but one day you might have a nice microphone,no?

I bought a hundred standard metal film types (good and well-known brand) instead and matched them,no biggie to find some pairs.It depends on how precise your dmm works,check its' manual.

Your choice.

Best regards,

Udo.